1. Technical Field
The present invention refers to an immersion probe for analysis of gases, which comprises a porous ceramic filter at its gas-collecting end.
2. Description of the Prior Art
Immersion probes for analysis of gases are now indispensable tools in the manufacture of metals, particularly important in the production of steel, wherein some specific gases are viewed as harmful elements. Because of this, it is necessary to monitor constantly the contents of these gases, as well as to adjust them at permitted levels. In this regard, the hydrogen content in molten steel in its liquid state is of extreme important, since certain non-permitted contents cause irreparable damages to the metal when the latter is in solid state.
Thus, the analysis of the amount of gases in molten metals is carried out by means of a disposable device called a probe, which is secured by a support and immersed into a bath of molten metal in a contained, which may be a metallurgical pot, furnace or another container whatever suitable for receiving molten metals. The probe has, at one of its ends, a porous ceramic filter that is associated to a gas sampling tube by addition of an adhesive material, usually cement or ceramic adhesive, which provides mechanical support for the porous ceramic filter in the gas sampling tube.
In this regard, in order to analyze the gas or the mixture of gases contained in the molten metal, a gas carrier known as high-purity Nitrogen is injected into the metal through an injection tube. The mixture of gases containing the high-purity Nitrogen is then extracted by suction through the immersion probe by means of the porous ceramic filter and sent subsequently to a meter through the gas-capturing tube, where the analysis of the mixture of gases takes place, preferably in a system with catharometer through heat conductivity of the gases.
Additionally, the operations of injecting the carrier gas into liquid steel an extraction of the mixture of gases contained therein are time-consuming operations and are carried out in an extremely aggressive environment due to, for instance, brutal thermal shocks, high temperatures, vibration, ferrostatic pressure, mechanical and chemical corrosion, among other factors. All these adversities require much from the immersion probe for gases, besides being dangers for the operator as well, and the stresses during the detection often reach limits that cause cracks and/or breaks in the porous ceramic filter, especially in the area of association between the gas sampling tube and the porous ceramic filter.
Thus, these cracks of the porous ceramic filter may be of various magnitudes, and there may even be total break thereof. Middle-size and large-size cracks may cause troubles during the detection and cause erratic readings of the value of gases contained in the steel. On the other hand, the break of the ceramic filter may allow the entry of liquid metal into the immersion probe and into the gas sampling tube, causing erratic measurements in the detection of gases, and so it is necessary to carry out a new detection operation by using a new probe, which prolongs the time of detecting gases, as well as increases the dangers for the operator.
In this regard, probes like those described are known from the prior art, as for example, the Brazilian patent PI 8806242, which describes and claims a probe, an apparatus and a method for the analysis of gases in molten metal. Another example of a probe for the analysis of gases in molten metal is also described in U.S. Pat. No. 6,216,526. This document describes a probe comprising a porous ceramic filter associated to a gas sampling tube, plus an adhesive material for mechanical support in this association, thus producing a sealing, but still with the same problems mentioned.
It should be noted that statistics demonstrate that errors in detecting the hydrogen contents may reach 20% of the read value, while the number of detection failures due to large cracks and/or break of the ceramic filter reaches 15%. The ideal value is 5% in both cases.